1. Field of the Invention
The invention relates to a method for cleaning vessels, particularly steam generators, in which solid deposits on the surfaces of the vessels are dissolved chemically and removed mechanically.
2. Description of the Prior Art
In steam generators, the heat transfer is inhibited by deposited corrosion products. In addition, enrichment of salts and copper compounds leads to further corrosion of the heating tubes in the steam generator. Consequently, it is most important, indeed almost essential, to at least periodically remove the encrustation on the vessels.
Up to now, two different cleaning methods, known generally as a mechanical cleaning method and a chemical cleaning method were employed to remove solids deposited on vessel surfaces. These two methods have been used separately, i.e. either the mechanical or the chemical method was used but not both. Most commonly, deposits have been removed by regular application of a mechanical cleaning method. However, this procedure is not entirely satisfactory because in the steam generator, hard encrustations remain, which are enriched by calcium salts and copper salts. A purely mechanical method therefore cleans the steam generator incompletely. With a chemical cleaning method, all deposits are dissolved chemically and are then separated either by precipitation, by filtration or by ion exchange, or are removed together with the solution. This requires considerable time and relatively many waste materials must be removed. Purely chemical cleaning of steam generators is therefore not economical because of the high cost.